This invention relates to an original method for non-invasive brain stimulation using a magnetic field. The earliest nomenclature is transcranial magnetic stimulation (TMS).
TMS is based on the principle of electromagnetic induction, whereby the cerebral cortex is stimulated as an outcome of the rapid discharge of current through a coil held over the scalp. This discharge induces an electric field surrounding the coil, which in turn induces current flow of a sufficient magnitude to depolarize and/or stimulate neurons in underlying tissue. The basic principle relates to cell membranes sustaining potential difference between intra- and extra-cellular space. An externally applied electric field may deviate the cell's membrane potential; that is, depolarize the membrane and hence activate excitable tissue. Electric fields suitable for neural stimulation can be generated non-invasively by applying electromagnetic induction. At this point, a majority of TMS research and treatment has been limited to the stimulation of the motor cortex area due to discernible effects being relegated only to that general locale. There are also a number of treatment and procedure difficulties relating to such areas as patient compatibility, discerning exact application, possibility of multiple action modalities, rationale of device, and most amenable target population.
Transcranial magnetic stimulation has been studied at precise and considerable length for at least the past 15 to 20 years; initial modern demonstrations by Barker, et al., in Sheffield, England, in 1985. (Origins of modern study—1960s,—Early concept formulation late 1800s) There has been improvement coming from several directions during the last 10 years. TMS did shift from continued research and theoretical investigation to actual application within specific and basic perimeters. A significant upgrade pertains to rapid transcranial magnetic stimulation (rTMS)—approximately one pulse every 0.10 to 0.50 seconds—involving using a figure-8 surface coil (a stimulating coil with two planar wings with opposing current directions; induces a better focused electric field than a single circular coil as was previously used) formulation in the mid 1990s and has been brought into play with the goal of treating the cognitive dysfunction of has been brought into play with the goal of treating the cognitive dysfunction of depression (George et. al., the Journal of Neuropsychiatry and Clinical Neurosciences, 8.373, 1996. Kolbinger et al., Human Psychopharmacology, 10:305, 1995).
TMS has several present and potential applications, in the domains of basic neuroscience research and of the treatment of brain disorders. Currently TMS delivery system and/or technique is rather rudimentary. The TMS stimulator is a wire-wound coil, typically shaped like a “B.” The B-shaped coil is placed against the scalp and held in place by a human clinician. This causes geographic and stability problems for both the patient and clinician. For the primary motor cortex and primary visual cortex (small sections of the total brain surface), proper positioning is established by the elicited response: muscle contractions when stimulating the primary motor cortex; illusory lights (phosphenes) when stimulating the primary visual cortex. In both of these areas, the effects are very sensitive to coil position and orientation. Many times false or skewed readings are the result. This, of course, makes utilization non-pragmatic, generally speaking. A more dependable method for determining the proper position and orientation of TMS coil position for brain areas deficient in immediately observable feedback is something that is required for further movement forward.
Of late (past 5-8 years) there has been a considerable increase related to multiple investigations of TMS potential toward at least some partial alleviation of cognitive dysfunction related to depression.    A. Barker A T, Jalinous R, Freeston I L. (1985) Non-invasive magnetic stimulation of human motor cortex. Lancet 1106-1107    B. George et. al., “Transcranial Magnetic Stimulation: A Neuropsychiatric Tool For The 21.sup.st Century,” J. Neuropsychiatry, vol. 8, No. 4:373-382 (1996).    C. Kolbinger H M, Hoflich G, Hufnagel A et al. (1995) Transcranial magnetic stimulation (TMS) in the treatment of major depression: a pilot study. Human Psychopharmacology 10: 305-310.